OFFSET
0,2
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
LINKS
Robert Price, Table of n, a(n) for n = 0..1000
Eric Weisstein's World of Mathematics, Elementary Cellular Automaton
Stephen Wolfram, A New Kind of Science
Index entries for linear recurrences with constant coefficients, signature (3,-3,3,-2).
FORMULA
From Colin Barker, Jan 17 2016 and Apr 16 2019: (Start)
a(n) = 3*a(n-1) - 3*a(n-2) + 3*a(n-3) - 2*a(n-4) for n > 3.
G.f.: (1-x+x^2) / ((1-x)*(1-2*x)*(1+x^2)).
(End)
a(n) = floor(6*2^n/5). - Karl V. Keller, Jr., Apr 12 2021
MATHEMATICA
rule=147; rows=20; ca=CellularAutomaton[rule, {{1}, 0}, rows-1, {All, All}]; (* Start with single black cell *) catri=Table[Take[ca[[k]], {rows-k+1, rows+k-1}], {k, 1, rows}]; (* Truncated list of each row *) mc=Table[catri[[k]][[k]], {k, 1, rows}]; (* Keep only middle cell from each row *) Table[FromDigits[Take[mc, k], 2], {k, 1, rows}] (* Binary Representation of Middle Column *)
PROG
(Python) print([6*2**n//5 for n in range(50)]) # Karl V. Keller, Jr., Apr 12 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Robert Price, Jan 17 2016
STATUS
approved